As a technique for cutting a planar object to be processed along a line to cut, there is one known as blade dicing method (see, for example, Patent Literature 1). The blade dicing method attaches the planar object to an expandable sheet stretched over an annular frame, secures it onto a mount table, and cuts the object along a line to cut with a cutting blade rotating at a high speed. Here, for preventing the frame surrounding the object from being damaged, the cutting blade is moved relative to the object only in an area on the inside of the frame.
On the other hand, as a laser processing method for cutting a planar object to be processed along a line to cut, there is one which attaches the planar object to an expandable sheet stretched over an annular frame, secures it onto a mount table, and irradiates the object with processing laser light while locating a converging point within the object with a converging lens, so as to form a modified region to become a starting point region for cutting within the object along the line to cut (see, for example, Patent Literature 2).
Unlike the blade dicing method, it is necessary for such a laser processing method to move the converging lens relative to the object beyond the frame. The following are the reasons therefor. For irradiating the object with the processing laser light in a state where the relative moving speed of the converging lens with respect to the object is constant, an acceleration distance by which the relative moving speed becomes constant is required to be added to the relative movement distance of the converging lens with respect to the object. Also, while there is a case where the object is cut along the line to cut from the modified region acting as a cutting start point by expanding the expandable sheet outward, for example, it is necessary for the frame to be made as small as possible with respect to the object in order to realize reliable cutting.
Patent Literature 1: Japanese Patent Application Laid-Open No. 2006-13312
Patent Literature 2: Japanese Patent Application Laid-Open No. 2004-273895